1. Field of the Invention
The present invention relates to a blower, and particularly, to a blower used in an over-the-range (OTR) microwave oven and the like and a design method of a discharge port thereof.
2. Description of the Conventional Art
In general, an OTR microwave oven is one of electric home appliances, which is installed on a wall surface of an upper space portion of a gas range which is installed in the kitchen, so as to be used for cooking using microwave in a cavity and for sucking/exhausting combustion gas and pollution air in the kitchen (i.e., performing a ventilation function) generated from the gas range installed under the OTR microwave oven using a blower installed therein.
FIG. 1 shows a typical type of the conventional OTR microwave oven, which will now briefly be explained as follows.
The conventional OTR microwave oven, as shown in FIG. 1, includes a main body 1 having a cavity (i.e., a cooking space) C for cooking by a microwave, an outer casing 3 receiving the main body 1 and having an exhaust passage 2 at both sides of the main body 1, and a blower 4 installed at a upper rear side of the main body 1.
A rotary tray 5 is rotatably installed inside the cavity C so as to rotate food taken in the cavity C. A magnetron 8 for generating microwave induced inwardly to the cavity C while cooking is installed at an outer side of the cavity C.
An air suction port 6 communicated with the exhaust passage 2 is positioned at a lower side of the outer casing 3, and an air discharge port 7 for discharging air to the exterior is formed on an upper surface of the outer casing 3. Here, according to a user's convenience, the air discharge port 7 may be connected to a ventilating duct of a building, and the like, through a connection duct (not shown), or be installed on the entire upper surface of the outer casing 3.
Such constructed conventional OTR microwave oven is installed above a gas range, and serves as a hood for ventilating smoke or smell generated when a user cooks using the gas range as well as performing the original function of the microwave oven.
The user opens a door (not shown) and puts food on a rotary tray 5 in the cavity C. The user then closes the door and presses an operating button of an adjustment plate (not shown). According to the this, the rotary tray 5 is rotated, which rotates the food thereon and simultaneously generates microwave from a magnetron 10. The microwave generated is induced inside the cavity C to cook food thereby, all of which is the original function of the microwave oven performed by the conventional OTR microwave oven.
Furthermore, in the conventional OTR microwave oven, when the user presses the hood operation button of the adjustment plate, the blower 4 installed in the microwave oven is driven so as to generate a suction force, by which combustion gas and pollution air generated when the user cooks using the gas range installed under the microwave oven, as indicated by a biased line in FIG. 1, are sucked through the air suction port 6 formed at a lower surface of the outer casing 3. The sucked air is discharged to the exterior through the air discharge port 7 formed at an upper surface of the outer casing 3, whereby the conventional OTR microwave oven serves as the hood for ventilating smoke or smell.
The blower 4 of the conventional OTR microwave oven, on the other hand, as shown in FIGS. 2 and 3, includes a bracket 22 respectively coupled to both sides of a motor 21 positioned in the center, a centrifugal fan 23 coupled to a rotary shaft (not shown) protruded outwardly from the center portion of each bracket 22, and a cylindrical fan housing 24 of which one side is fixed to the bracket 22 and covering the outside of the centrifugal fan 23.
The fan housing 24 is provided with a suction port 25 for sucking external air, and a discharge port 26 formed in a perpendicular direction of the suction port 25, for discharging air sucked through the suction port 25.
A cut-off portion 17 for guiding discharged air is protrudingly-formed at one side of the discharge port 26.
In the conventional blower 4 which has the configuration as aforementioned, when power is applied, the motor 21 is rotated and thus the centrifugal fan 23 axially coupled to the motor 21 is rotated as well. The suction force is generated by the rotation of the centrifugal fan 23 to suck external air inwardly through the suction port 25 formed at one side of each fan housing 24.
The air sucked into the fan housing 24 through the suction port 25 is discharged through the discharge port 26 formed in the perpendicular direction of the suction port 25 by the rotation force of the centrifugal fan 23.
However, in the conventional blower 4, an air flow formed by the rotation of the centrifugal fan 23 forms a large loss area due to growth of a boundary layer at an edge portion of the discharge port 26. The air flow loss in the discharge port 26 may impede air volume and also increase noise.
A scheme for forming the cut-off portion of the discharge port 26 in ‘V’-shape has been proposed as a way to solve the problem which has been applied by this assignee and disclosed in U.S. Pat. No. 6,200,093.
However, in the type of forming the discharge port in the ‘V’-shape as proposed by this assignee, a flow rate discharge through the discharge port has uniformly been distributed to thus reduce noise to some degree, but a discharged air volume has unfortunately been reduced.